Port to PyQt6

Author: manateelazycat

buffer.py

@@ -20,8 +20,8 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 
-from PyQt5 import QtCore
-from PyQt5.QtCore import QUrl, QFileSystemWatcher, QTimer
+from PyQt6 import QtCore
+from PyQt6.QtCore import QUrl, QFileSystemWatcher, QTimer
 from retrying import retry
 from core.webengine import BrowserBuffer
 from core.utils import get_free_port, message_to_emacs, eval_in_emacs, get_emacs_var, get_app_dark_mode